1. Technical Field
The present invention relates generally to a hydraulic cylinder used to control the position of a sprayer boom.
2. Description of Related Art
The high crop yields of modern agribusiness require large amounts of fertilizers, pesticides, and herbicides. Dispersing these chemicals onto high acreage fields requires specialized machines. A ubiquitous example of such a machine is the self-propelled sprayer.
As illustrated in FIG. 1, a common design for a self-propelled sprayer includes a dedicated chassis 1 with a tank 20, booms 30, and nozzles 40 connected to the booms 30. The tank 20 contains fluid such as fertilizers, pesticides, and herbicides. Booms 30 extend outward from the sides of the dedicated chassis 1. Boom plumbing runs along the length of the booms 30, and contains a plurality of nozzles spaced apart along the length of the booms 30.
In operation, as the dedicated chassis 1 crosses a field, fluid is pumped from the tank 20 to the sprayers 40 along the booms 30, and out through the nozzles. This allows the self-propelled sprayer to distribute the fluid along a relatively wide path. The length of conventional booms 30 may vary from, for example 6 meters (18 feet) up to 46 meters (150 feet). It is not practical for the booms 30 of the self-propelled sprayer to always be in the extended position. This would make it difficult to store, maneuver or transport the self-propelled sprayer around buildings and on the road. Therefore, the booms 30 are designed to swing or fold into a more compact position.
Movement of the booms 30 is accomplished using hydraulic cylinders. By regulating fluid pressure within the cylinders, the boom can be easily moved. When the self-propelled sprayer is operating, the booms 30 are extended.
The relatively large width of path covered by a self-propelled sprayer makes accidental contact between the booms and external objects inevitable. When a boom 30 impacts an object such as a tree, the ground, a power pole, or a rock, extensive damage can occur if the boom 30 is held rigid.
To address the problem of collisions between the boom and other objects, breakaway cylinders have been employed. FIG. 2 illustrates one conventional design of a boom frame assembly 50, having a breakaway cylinder 70 separate from main swing cylinders 60a, 60b. The main swing cylinders 60a, 60b are attached to the boom frame 55 to regulate the position of the booms. Each of the two main cylinders 60a, 60b is employed to regulate one of the booms. The breakaway cylinder 70 is coupled to the main swing cylinders 60. Unlike the main swing cylinders 60, the breakaway cylinder 70 is adapted to be independently controlled, allowing for the breakaway cylinder 70 to compress. Thus, the force from the boom striking an object causes breakaway cylinder 70 to compress, which enables the boom to swing rearward. This lessens the impact from the collision and reduces or minimizes damage to the boom.
It would be beneficial to reduce the number of separate cylinders that are required in a boom assembly and increase distance that the breakaway cylinder is able to compress to improve impact absorption.